Halogenated hydrocarbons such as Freon, designated R113 and manufactured by the DuPont Chemical Company, are used in high-power rated transformers for cooling the transformer windings. A gas insulated transformer contains a high-pressure transformer tank filled with sulfur hexafluoride (SF.sub.6) or carbon hexafluoride (C.sub.2 F.sub.6) to provide electrical insulation to the transformer windings. A quantity of Freon coolant is piped through the transformer windings in a closed piping system that connects with a heat exchanger and a pump to return the cooled Freon back to the windings. The presence of SF.sub.6 gas in the Freon line could cause cavitation and interfere with the transport coolant properties of the Freon coolant.
A vaporization cooled transformer, such as described within U.S. patent application Ser. No. 843,676, filed Oct. 19, 1977, utilizes a quantity of Freon coolant to cool and insulate transformer windings at the operating temperature of the transformer. A quantity of SF.sub.6 gas can be employed in the space above the Freon coolant to provide dielectric insulation to the windings during transformer start-up when the Freon is totally in its liquid phase. Determining the quantity of SF.sub.6 that becomes dissolved within the Freon coolant provides an indication as to the severity of leaks that may develop during transformer operation.
The purpose of this invention is to provide a simple and efficient means for monitoring the concentration of SF.sub.6 in Freon during transformer operation without having to disconnect the transformer from operation during the determination process.